1. Field of the Invention
The present invention is generally related to a stent having a constant stiffness along the length of the stent, and a method for manufacturing a stent having a constant stiffness along the length of the stent.
2. Background of the Invention
A stent is typically a hollow, generally cylindrical device that is deployed in a body lumen from a radially contracted configuration into a radially expanded configuration, which allows it to contact and support a vessel wall. A plastically deformable stent can be implanted during an angioplasty procedure by using a delivery system that includes a balloon catheter bearing a compressed or “crimped” stent, which has been loaded onto the balloon. The stent radially expands as the balloon is inflated, forcing the stent into contact with the body lumen, thereby forming a support for the vessel wall. Deployment is effected after the stent has been introduced percutaneously, transported transluminally, and positioned at a desired location by means of the balloon catheter.
Stents may be formed from wire(s), may be cut from a tube, or may be cut from a sheet of material and then rolled into a tube-like structure. While some stents may include a plurality of connected rings that are substantially parallel to each other and are oriented substantially perpendicular to a longitudinal axis of the stent, others may include a helical coil that is wrapped around the longitudinal axis at a non-perpendicular angle.
When tracking stents on a delivery system in the lumen to a deployment site, if the stiffness of the stent varies along the length of the stent, an increase in end flaring and/or strut/crown lifting may occur. Specifically, when there is a transition from a lower stiffness to a higher stiffness, or vice versa, a “kink” point may occur at the transition. The result of the “kink” point is that the parts of the surrounding structure of the stent may interfere with each other and cause lifting. This may also occur at the end of the stent with the transition of the delivery system, which has a low stiffness, to the stent, which has a high stiffness.